Field of the Invention
This invention relates in device packages with openings in the encapsulant.
Description of the Related Art
A packaged device includes a device such as a semiconductor die or standalone electronic device encapsulated in an encapsulant that allows it to be utilized in a system (e.g. an electronic system such as a computer, phone, laptop, or other system utilizing a device such as an automobile, appliance, robotic equipment etc.). The packaged device may include external terminals (e.g. leads, pads, bumps) for providing communication signal lines and power to the device.
With some packaged devices, it is desirable to have an opening in the encapsulant to expose portions of the device for utilization in the system. For example, some types of sensors include surfaces that need to be exposed to accurately sense the desired condition. As an example, a radiation sensor includes a surface to sense alpha particle radiation. In another example, an optical communication device (e.g. photo diode) needs to be free of encapsulant for proper operation. In yet another example, an ion sensor, such as an ion selective field effect transistor or ion sensitive field effect transistor (ISFET), needs to have the sensor region on a device to be free of encapsulant in order to determine is a particular ion is present in the sensing environment.
Such openings can be formed with film assisted molding techniques where a structure, film, or other substance is placed in the desired location of the encapsulant opening such that the encapsulant does not occupy the area of the desired opening during encapsulation. After the encapsulating process is complete, the structure, film, or substance is removed from the encapsulated device. In another example, a mold press wall may include a non-planar surface having a portion that extends to the device during the encapsulating process. The extending portion of the mold press wall contacts the device (or a film on the device) during encapsulation to form an opening over the device.
In other embodiments, the device may be inserted into a prefabricated structure that includes a cavity and a leadframe. The prefabricated cavity may be defined by a pre-molded polymer or ceramic structure with side walls that are physically coupled to the leadframe. With some prefabricated structures, a lid with an opening may be utilized to close the cavity after device placement where the lid exposes the desired region of the device inside the prefabricated structure.
The use of the same reference symbols in different drawings indicates identical items unless otherwise noted. The Figures are not necessarily drawn to scale.